It feels like much plastic since you touch each one, but it's a very tiny amount if you weigh your monthly usage.

With a French Press, you don't have to buy and throw away a constant stream of paper filters.

If you're making a single cup (~250mL) why do you need to heat 1000mL of water?

Pretty much. I used my keurig this way for a few years until i realized I'm really not using pods and am only using it for hot water to make tea (via normal steeping). If you brew coffee and then use it for something right after I don't recall there being much coffee taste, but you could probably run a small cup setting to flush things in the pod area a bit if needed.

I've since switched to a Zojirushi water boiler which I adore, especially after learning my keurig wasn't getting hot enough to really brew the tea well.

I used to use my Senseo to make ramen so ¯\_(ツ)_/¯